January
2010
, Volume
23
, Number
1
Pages
58
-
66
Authors
Anita S. Bek,1,2
Jørgen Sauer,1,3
Mikkel B. Thygesen,1,3
Jens Ø. Duus,4
Bent O. Petersen,4
Søren Thirup,1,2
Euan James,5
Knud J. Jensen,1,3
Jens Stougaard,1,2 and
Simona Radutoiu1,2
Affiliations
1Centre for Carbohydrate Recognition and Signalling (CARB) and 2Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10, Aarhus 8000 C, Denmark; 3IGM, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark; 4Carlsberg Laboratory, Gamle Carlsberg Vej 10, 2500 Copenhagen Valby, Denmark; 5EPI Division, Scottish Crop Research Institute (SCRI) Invergowrie, Dundee DD2 5DA, U.K.
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RelatedArticle
Accepted 9 September 2009.
Abstract
Formation of functional nodules is a complex process depending on host--microsymbiont compatibility in all developmental stages. This report uses the contrasting symbiotic phenotypes of Lotus japonicus and L. pedunculatus, inoculated with Mesorhizobium loti or the Bradyrhizobium sp. (Lotus), to investigate the role of Nod factor structure and Nod factor receptors (NFR) for rhizobial recognition, infection thread progression, and bacterial persistence within nodule cells. A key contribution was the use of 800 MHz nuclear magnetic resonance spectroscopy and ultrahigh-performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry for Nod factor analysis. The Nod factor decorations at the nonreducing end differ between Bradyrhizobium sp. (Lotus) and M. loti, and the NFR1/NFR5 extracellular regions of L. pedunculatus and L. japonicus were found to vary in amino acid composition. Genetic transformation experiments using chimeric and wild-type receptors showed that both receptor variants recognize the structurally different Nod factors but the later symbiotic phenotype remained unchanged. These results highlight the importance of additional checkpoints during nitrogen-fixing symbiosis and define several amino acids in the LysM domains as expendable for perception of the two differentially carbamoylated Nod factors.
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© 2010 The American Phytopathological Society